1. Field of the Invention
The present invention is directed to integrating optics on the wafer level with an active element, particularly for use with magneto-optic heads.
2. Description of Related Art
Magneto-optical heads are used to read current high-density magneto-optic media. In particular, a magnetic coil is used to apply a magnetic field to the media and light is then also delivered to the media to write to the media. The light is also used to read from the media in accordance with the altered characteristics of the media from the application of the magnetic field and light.
An example of such a configuration is shown in FIG. 1. In FIG. 1, an optical fiber 8 delivers light to the head. The head includes a slider block 10 which has an objective lens 12 mounted on a side thereof. A mirror 9, also mounted on the side of the sliderblock 10, directs light from the optical fiber 8 onto the objective lens 12. A magnetic coil 14, aligned with the lens 12, is also mounted on the side of the slider block 10. The head sits on top of an air bearing sandwich 16 which is between the head and the media 18. The slider block 10 allows the head to slide across the media 18 and read from or write to the media 18.
The height of the slider block 10 is limited, typically to between 500-1500 microns, and is desirably as small as possible. Therefore, the number of lenses which could be mounted on the slider block is also limited. Additionally, alignment of more than one lens on the slider block is difficult. Further, due to the small spot required, the optics or overall optical system of the head need to have a high numerical aperture, preferably greater than 0.6. This is difficult to achieve in a single objective lens due to the large sag associated therewith. The overall head is thus difficult to assemble and not readily suited to mass production.
Therefore, it is an object of the present invention to provide a slider block having an active element, i.e., an element having a characteristic which changes in response to an applied field, integrated thereon which substantially overcomes one or more of the problems due to the limitations and disadvantages of the related art. Such elements include a magnetic coil, a light source, a detector, etc.
It is a further object of the present invention to integrate multiple optical elements and a slider block having the active element integrated thereon as well. It is a further object of the present invention to manufacture the objects on a wafer level, bond a plurality of wafers together and provide the active element on a bottom surface of a bottom wafer.
At least one of the above and other advantages may be realized by providing an integrated micro-optical system including a die formed from more than one wafer bonded together, each wafer having a top surface and a bottom surface, bonded wafers being diced to yield multiple dies and an active element having a characteristic which changes in response to an applied field, integrated on a bottom surface of the die, optical elements being formed on more than one surface of the die.
The active element may be a thin film conductor whose magnetic properties change when a current is applied thereto. The active element may be integrated as an array of active elements on the bottom wafer before the bonded wafers are diced. The die may be formed from two wafers and optical elements are formed on a top surface and a bottom surface of a top wafer and a top surface of the bottom wafer. The die may include a high numerical aperture optical system.
The bottom wafer of the more than one wafer may have a higher index of refraction than other wafers. There may be no optical elements on a bottom wafer of the die. The bottom surface of the die may further include features for facilitating sliding of the integrated micro-optical system etched thereon. The bottom wafer of the die may have a refractive element formed in a material of high numerical aperture. Metal portions serving as apertures may be integrated on at least one of the surfaces of the die.
A layer of material deposited on the bottom surface of the bottom wafer before the active element is integrated thereon. An optical element may be formed on the bottom surface of the bottom wafer, wherein the layer has a refractive index that is different from the refractive index of the bottom wafer. The layer may be deposited in accordance with a difference between a desired thickness and a measured thickness.
A monitoring optical system may be formed on each surface of the wafer containing an optical element. The spacing between wafers may be varied in accordance with a difference between a measured thickness of a wafer and a desired thickness of a wafer.
A top surface of the die may be etched and coated with a reflective coating to direct light onto the optical elements. A further substrate may be mounted on top of the top of the die having a MEMS mirror therein. An insertion point may be provided on the die for receiving an optical fiber therein. The insertion point may be on a side of the die and the system further includes a reflector for redirecting light output by the fiber.
A refractive element in the die may be a spherical lens and the die further includes a compensating element which compensates for aberrations exhibited by the spherical lens. The compensating element may be on a surface immediately adjacent the spherical lens. The compensating element may be a diffractive element. The refractive element may be an aspheric lens. The die may include at least one additional refractive element, all refractive elements of the die being formed in material having a high numerical aperture.
At least one of the above and other advantages may be realized by providing an integrated micro-optical apparatus including a die formed from more than one wafer bonded together, each wafer having a top surface and a bottom surface, bonded wafers being diced to yield multiple die, at least two optical elements being formed on respective surfaces of each die, at least one of the at least two optical elements being a refractive element, a resulting optical system of each die having a high numerical aperture.
The refractive element may be a spherical lens and the die further includes a compensating element which compensates for aberrations exhibited by the spherical lens. The compensating element may be on a surface immediately adjacent the spherical lens. The compensating element may be a diffractive element. The refractive element may be an aspheric lens.
The die may include at least one additional refractive element, all refractive elements of the die being formed in material having a high numerical aperture. The refractive element may be on a bottom wafer and of a material having a higher refractive index than that of the bottom wafer.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.